A projection screen can have a mask in the form of a mask foil and a retaining frame for this mask foil which are subjected to a thermal stress in operation by a high-energy image forming medium or beam, for example, ions, electrons or X-rays. Regions permeable to the image-forming radiation, e.g. openings, are present in the mask foil.
The mask foil is advantageously combined with a metallic retaining frame.
Considerable distortions in the mask foil can be generated by a thermal stress applied to the mask foil, e.g. by the image-forming beam particularly when the mask foil does not have the same effective thickness at all points. Thus the thermal stressing of a mask foil of uniform thickness can lead to distortions of the openings in the foil so that the methods of thermal stressing can be used generally only for test masks in 1:1 ion or electron shadowography and/or in ion or electron beam image demagnifying projection.